Who among the following was the first person to scale Mount Everest without supplemental oxygen?

Who among the following was the first person to scale Mount Everest without supplemental oxygen? [A]Terence Bannon [B]Duncan Chessell [C]Reinhold Messner [D]Jean Troillet Show Answer Reinhold Messner Reinhold Messner (German) is the first person to scale Mount Everest without supplemental oxygen, along with Peter Habeler in 1978. He is also first climber to ascend all